This invention relates to insoles for footwear, to the adjacent outer sole and to shoe lasts which are needed in the manufacture of footwear. The insole has always been an important component of any good shoe. Decades ago, it was made from leather, but today the majority of all insoles are made from paper-based materials. Lately, some shoe manufacturers use insoles which are partially or wholly molded from plastic materials. It can be expected that molded insoles will be increasingly used in the near future in the same way that molded outer soles have been increasingly used in the past few years.
Recently, the outer sole and the heel of a shoe are molded as one piece and are well-known as unit soles. If made in large quantities, these unit soles are economically advatangeous but, they are precision-made and therefore it is necessary that the adjacent components such as upper and insole are also precisely made prior to assembly. Correct alignment and matching is of utmost importance when asembling mass-produced components. For instance, great care must be taken when the outer sole is attached to the lasted shoe, i.e., it must be in correct alignment with the insole of the shoe. If molded shoe components are used at assembly, subsequent touch-up or finishing operations should not be necessary, otherwise some of the advantages of molded shoe components are lost. So far, a shoe assembler has to have experience and skill as to position accurately the insole against the bottom of the last and the outer sole against the lasted shoe or insole respectively. But, even when the assembler has correctly positioned the outer sole to the lasted shoe, there is a chance that the outer sole might slip away from its predetermined position when the outer sole is joined to the shoe in the sole attaching press. This can happen when the cement is yet too slippery or when the shoe is improperly located on the sole pad. This problem will be eliminated when the insole has an aligning protrusion which fits a correspondingly disposed cavity in the outer sole assuring an accurate predetermined position at the assembly of the outer sole.
In conventional shoemaking the shank portion of an insole is often made stiff by attaching a steel shank to it. Usually, the steel shank is attached to the insole by means of staples. The stiffening effect can be accomplished by molding a reinforcement rib to the insole. Again, the operation of attaching the steel shank to the insole is hereby eliminated.
A rather new way of lasting shoes is string-lasting, so called because string is used to pull the lasting margin of an upper over the edge of an insole. In this method of lasting shoes, the string is slideably attached all around the edge of the shoe upper. When the upper is to be lasted over the last, the ends of the string are pulled, forcing the edge of the upper onto the bottom of the last. Due to the shape of a last, the maximum pulling force is applied to the upper at its toe and heel end where good lasting is accomplished. In order to accomplish proper lasting of the sides of the shoe as well, the operator pulls the upper over the sides by means of a pair of lasting pincers and drives a few staples to hold the lasting margin in place. However, by means of lasting hooks positioned on our novel insole it is possible to eliminate driven fasteners and improve the string lasting operation considerably. After the heel and toe have been properly lasted, but the sides of the upper only partially pulled over, the operator grabs the string by means of a special tool, pulls up the sides of the upper and fastens them by drawing the string behind the lasting hooks. This way, there is no danger that later on a metal fastener might get into the inside of the shoe.
In another novel lasting operation the lasting hooks are located all around the molded insole. When the upper is prepared for lasting, holes are punched through the lasting margin of the upper identical to the number of lasting hooks of the corresponding insole. The upper is pulled manually over the last and held in place by engaging the lasting margin through the holes to the lasting hooks. This method of lasting is suitable for soft fabric uppers or for those uppers which can be softened sufficiently prior to lasting. Though limited to inexpensive footwear, it eliminates the need of all costly lasting machinery.
For a long time it has been the desire of the shoe industry to attach the insole to the bottom of a last without using tacks or other metals fasteners, and prior art has taught several ways of doing so. But all suggestions seem to have some disadvantages since until now the majority of all insoles are attached to the last by tacks. It is believed that our improved last is a real breakthrough in tackless insole fastening. The improvement of a shoe last comprises two registration pins, one of them firmly located in the forepart area of the last, the other one resiliently located in the heel area of the last. The ends of the registration pins stick out of the bottom of the last and engage their corresponding registration holes in the insole. When the insole is attached to the last, it is first pushed onto the resilient registration pin in the heel end of the last, then moved forward toward the toe end overcoming the force of resiliency, and finally slipped onto the registration pin in the forepart area of the last. Now, the insole is firmly held in place since the force of the compressed spring keeps the insole under tension, and the conically shaped ends of the pins prevent any slippage of the insole away from the last bottom.
It is an objective of this invention to minimize the skill of the sole attaching operator who is responsible for the accurate positioning of the outer sole relative to the insole. This is accomplished by molded aligning protrusions on the insole which fit correspondingly disposed cavities in the outer sole. At assembly, these aligning protrusions will guide the outer sole into its predetermined, correct position.
It is another objective of this invention to manufacture an insole which receives in one molding operation some or all of those features which are pointed out in this specification, i.e. aligning protrusions, registration holes, shank reinforcement rib, lasting hooks, arch support, and a contour which fits the contour of the bottom of the last. This way it is possible to eliminate several individual operations and keep the manufacturing costs down.
It is a further objective of this invention to improve the method of string-lasting. In this lasting method there are hardly any forces available to pull-over the sides of a shoe upper by a string. After the sides of the upper have been pulled over manually, the lasting margin of the upper can be held in place by the engagement of the lasting hooks and the string which is slideably attached to the lasting margin.
Another aim of this invention is the development of a new lasting method. This lasting method will be particularly suitable for fabric uppers or other soft uppers. When using this method of lasting, lasting hooks are located all around the insole and the upper is prepared in such a way that its lasting margin has a plurality of holes which in number and location correspond to the lasting hooks of the insole. At assembly, the upper is pulled over by manual lasting pincers and connected to the insole by tying it through the holes behind the lasting hooks. Of course, insole and upper can be precemented in any conventional way.
It is another aim of this invention to ease the locating and attaching of the insole to the bottom of a last without using tacks or other driven fasteners. The last bottom is equipped with two registration pins, one firmly located in the toe area, the other one resiliently located in the heel area. The insole has two corresponding registration holes. When the insole is attached to the last, it is first pushed onto the resilient pin in the heel area, then moved toward the toe against a spring force until the toe hole engages the pin in the toe area.-- The above and other features of this invention will now be described in more detail with reference to the accompanying drawings. It is to be understood that the particular embodiments referred to above and herein described are deliniated for illustration of the invention only and are not to be construed as limiting the scope thereof.